Twelve years and two weeks since they went into Afghanistan, Australian forces - or most of them - are finally coming home.

Forty died in those years, 261 were seriously wounded and billions of dollars spent. And the psychological toll can't possibly be known yet.

So, was it worth it?

I've asked that question many times. I asked it first in the future tense, before they even went in, when then Prime Minister John Howard committed Australia to war without reference to Cabinet or constituents, in Washington DC on September 11, 2001.

Like other colleagues in the media, l was there at the time, reporting on John Howard's visit, staying in a hotel next to the White House within line of sight of the burning Pentagon and terribly worried for friends in New York.

Nevertheless, the adrenalin-fuelled talk of retribution worried me deeply. It was clear the attacks could not go unanswered but what should the response be, exactly? I felt the US needed to slow its breathing and think.

In a newspaper column two days after that terrible Tuesday morning, l asked rhetorically whether as a nation we shouldn't also take a breath and be certain - or as certain as we could be – about what exactly we, through our Prime Minister, were joining. When l got home to Australia, shellshocked at what had happened to America and at being in the midst of it, l got a letter calling me a traitor.

The truth is, Australia wasn't at all certain about what it was joining and, in my opinion, should have paused long enough to demand that the American Government make more than a plan for invasion. Neither thing was done.

Federal Parliament never even debated the Afghan commitment until a couple of years ago, when the Government was making a plan to withdraw.

There isn't always time for advance parliamentary debate. But time should be made for consideration.

It now appears that the US Government in 2001 did not know what it was trying to achieve in more than a general sense. The military strategy was a mess.

The twin objectives were to remove the Taliban from office and to rout al-Qaeda. But they wrongly thought it would be straightforward and that the job was done when it wasn't. Too little time was spent considering Afghanistan's feudal history, assessing regional allegiances (especially tribal connections in Pakistan) and understanding the possible consequences should things drag on.

Armies at least as great as theirs had been chased out of Afghanistan before.

John Howard has said in the years since then that, although he has no regrets about his decision-making, he wanted Australia's commitment to be sharp and short. In that respect, he didn't achieve his objective either.

He also acknowledged what 5th century Chinese military strategist Sun Tzu noted in 'The Art of War' - that popular support for any war wanes if it drags on. And then there's always a risk that nobody wins.

So here we are, turning off the lights at the base at Tarin Kowt only now, 12 years on, after what has become Australia's longest military conflict.

And back to that question - was it worth it?

Governments of every stripe will always say it was. Who would ever volunteer to fight for their country again if their own government suggested they could be risking their lives for nought?

Those who saw Afghanistan before coalition forces went in will also tell you it was worth it. They tell stories of seeing turbanned bodies swinging from lamp posts in a town square, in public retribution for some tribal wrong.

Afghanistan has not been used as the base for a successful mass terrorist attack on the West since September 11.

And lots of girls go to school now. In fact, children in general go to school in Uruzgan in far greater numbers than before. Boys and young men have learned trades. As one local tribal elder told me in

2011 as we sat cross-legged on the ground in a tent in the Baluchi Valley surrounded by all the male members of the village: "We don't want to be shepherds forever."

And hard-headed military planners will also tell you that having had more than 20,000 Australian personnel gain operational experience in a war zone is hugely valuable to the ADF in future.

Was all that worth all the dollars spent and all the lives lost - including those 40 Australians and many, many Afghans?

And what about the scarred souls who've come home trying to reconcile what they've seen with where they now are?

I spoke to a chaplain whose energy is spent supporting others but who forever carries the burden of trips to the morgue and of knowing exactly what happened to three Australian mates, gunned down, "green-on-blue", by an Afghan colleague with a semi-automatic rifle.

Earlier this year, back home in Canberra, l sat with one senior officer as he talked about his experiences and wept.

On two of my own three visits to Afghanistan l witnessed young men and women dealing with being told that their mates - a young sniper in 2011 and a Special Forces engineer in 2012 – had just been blown up. I watched flag-draped coffins carried on and off aircraft in a slow march, as the piper played. The trauma runs deep.

In some ways, the answer to the question depends upon what happens to Afghanistan now and whether the fears of a full resumption of the brutal old feudalism will be realised, in the face of Afghan security forces' patchy capability to stop it.

But for some, even inside the ADF, and even among those who believe deeply in the rightness of what they were doing, there is only one answer.

I asked a military officer the question in the past few days.

"Was it worth it?"

He shook his head. "No way," he said. "It wasn't."

Karen Middleton reported for SBS from Afghanistan in 2007 with cameraman/editor Jamie Kidston and in 2011 and 2012 with cameraman/editor Jeff Kehl. She is the author of a book detailing the political backstory to Australia's Afghanistan commitment, 'An Unwinnable War'.